In a solid-state light-emitting element which emits light in a region whose refractive index is higher than that of the air, part of light emitted in the inside of the light-emitting element is totally reflected at an interface with the air in a certain condition. As a result, efficiency in extracting light from the inside of the solid-state light-emitting element to the air side does not reach 100%.
For solving this problem, a structure in which a structure body (e.g., an uneven structure) is formed on a surface of a solid-state light-emitting element has been reported.
For example, Non-Patent Document 1 discloses a structure in which a high refractive index glass substrate and a high refractive index lens are combined and a structure in which an uneven structure is provided at an interface between a high refractive index glass substrate and the air, where light extraction efficiency of a light-emitting element is improved.